238 



DISLOCATIONS OF THE SILURIAN ROCKS. 



An axis of elevation ranging south-west and north-east, (from Wigmore to Ludlow,) 

 has elevated the Ludlow rocks into that remarkable promontory, the strata of which 

 dip to the north, east, and south-east. The elevatory forces having acted with the 

 greatest intensity along the interior or axis of the promontory, the shale of the Wen- 

 lock formation has been there brought up (PL 31. f. 5.) ; and being of less firm struc- 

 ture than the younger strata forming the external ridges, has been worn into a deep 

 valley in which there are only a few low hills. Towards the extreme point of the pro- 

 montory on which the castle of Ludlow stands, the intensity of the elevatory action 

 seems to have diminished, the youngest member of the Silurian System being alone 

 apparent, dipping under the Old Red Sandstone. (See Map.) This elevated mass is 

 indeed a fine example of a valley of elevation, and like most of the tracts so called, 

 it is strictly also a valley of denudation ; the lowest strata having been deeply ex- 

 cavated, leaving in the centre a level flat called Wigmore Lake, surrounded by the vil- 

 lages of Aston, Leinthall Starkes, Wigmore, and Burrington. This subject of valleys 

 of elevation, will be so amply illustrated in a subsequent chapter on the valley of 

 Woolhope, that it is here unnecessary to dwell further on the phenomena ; and the 

 probable condition of this depression in more recent epochs, will be spoken of under 

 the head of alluvial phenomena in the concluding chapters. In the meantime I may 

 observe, that this tract conveys to the geologist a clear conception of the abrupt manner 

 in which elevatory forces have affected the strata, particularly when viewed from the 

 high grounds of St. Mary's Knoll and the Vinnals, where two sides of the promontory 

 meet at an acute angle. On one side (see PL 31. fig. 5.) is the sharp ridge of Brindg- 

 wood Chase, composed of the Ludlow rocks dipping north at angles of 30°, and beneath 

 this escarpment a lower line of knolls, occupied by the Wenlock limestone and shale 

 extending to Burrington, the strata passing under the Ludlow rocks. On the other 

 or south-eastern face of the promontory, the movement has not been of this simple 

 character, but has produced a double system of ridges, in which the Ludlow rocks and 

 Wenlock limestone are each repeated, between an outer ridge ranging by Orelton 

 Common and Croft Ambrey, and an inner ridge occupying Gatley Coppice. In the 

 escarpment of the outer ridge, the angle of inclination increases with the height of the 

 hills, for at White way Head the beds of Aymestry limestone dip 45° to the south-east. 

 (See vignette, p. 241.) A section across this promontory from north to south, as ex- 

 pressed in PL 31. f. 5., explains more intelligibly than pages of writing, the relations 

 of this interesting tract, which in geological language may be called a saddle, having 

 a double flap on the south-eastern, and a single on the northern side. Although 

 in general the strata of the Ludlow rocks dip outwards from this promontory, passing 

 conformably and at low angles beneath the Old Red Sandstone, there are some ex- 

 ceptions to this rule, caused by partial dismemberments. Such, for example, are seen 

 in several undulating knolls near Richard's Castle, and at the " Bone Well" near that 

 village, where a mass of the rock is thrown across the general direction of the strata, 



